Can I plug my APC Rack-Mount Power Distribution Unit (Rack PDU) into a feed receptacle located in the under floor plenum? (Also applicable to Configurable & Modular Power Distribution)
Yes, provided the installation conforms to NFPA 70 the National Electric Code requirements as stated in Article 645 Information technology equipment.
With the 2008 Edition (and subsequently the 2011 Edition), Article 645.5 clearly states that cord-and-plug connections and certain cable types are allowed under raised floors, provided certain conditions are met. Following are excerpts from the 2008 Edition of the Code. Refer to the complete section of the applicable edition of the NEC for your locality.
645.5 Supply Circuits and Interconnecting Cables
(B) Cord-and-Plug Connections. The data processing system shall be permitted to be connected to a branch circuit by any of the following listed means:
(1) Flexible cord and attachment plug cap not to exceed 4.5 m (15 ft).
(2) Cord set assembly, where run on the surface of the floor, shall be protected against physical damage.
(D) Under Raised Floors. Power cables, communications cables, connecting cables, interconnecting cables, cord-and-plug connections, and receptacles associated with the information technology equipment shall be permitted under a raised floor, provided the following conditions are met:
(1) The raised floor is of suitable construction, and the area under the floor is accessible.
(2) The branch-circuit supply conductors to receptacles or field-wired equipment are in rigid metal conduit, rigid nonmetallic conduit, intermediate metal conduit, electrical metallic tubing, electrical nonmetallic tubing, metal wireway, nonmetallic wireway, surface metal raceway with metal cover, nonmetallic surface raceway, flexible metal conduit, liquidtight flexible metal conduit, or liquidtight flexible nonmetallic conduit, Type MI cable, Type MC cable, or Type AC cable. These supply conductors shall be installed in accordance with the requirements of 300.11.
(3) Supply cords of listed information technology equipment in accordance with 645.5(B).
(6) "Cables," shall be listed as Type DP. Type DP cable having adequate fire resistant characteristics suitable for use under raised floors of an information technology equipment room.
Rack Power Distribution
All of APC's Rack PDUs are UL Listed and as such meet all requirements for NEC 645 ITE data center installations. Prior to the 2008 Edition of the NEC, cord-and-plug connections under the raised floor were not explicitly identified in the 2005 Edition of the Code. However, based on the following code sections, these cord-and-plug connections of APC Rack PDUs are acceptable. 1) per 645.4(3) the equipment is UL Listed 2) per 645.5(B)(1) the flexible cord and attachment plug cap do not exceed 15 ft. 3) per 645.5(D)(2) branch-circuit supply conductors to receptacles are properly installed in accordance with 300.11 4) 645.5(D)(5) specifically relates to "cables" used under the raised floor, and not "flexible cord" as is the IT equipment power cord.
Making Power Connections to Rack PDUs Using Flexible Conduit
Some installations use wiring in flexible conduit (i.e. Sealtite) that is directly attached to a mating connector body for making the power connection to Rack PDUs. Any US installation must use methods that conform to NFPA 70 Article 300.
For 50A Rack PDUs that have CS8365 Hubbell style connector, Hubbell has a mating Pro-series connector body that can be attached directly to flexible conduit fittings. We recommend using a Hubbell Pro connector (CS8364L) with a 1/2" (H050) or 3/4" (H075) seal tight connector.
Configurable and Modular Power Distribution
Power cables from APC Configurable and Modular Power Distribution units are Type DP-1 TC-ER tray cable and per 645.5(D)(6) and Table 645-5 are allowed under raised floors.